Joins & APPLY
- INNER JOIN β Join two tables with matching keys; basic patterns.
- OUTER JOINs β LEFT/RIGHT/FULL joins, handling unmatched rows.
- CROSS/OUTER APPLY β Per-row subqueries/TVFs; choose CROSS vs OUTER APPLY.
- π§ Join Strategies β Hash, merge, and nested loops β recognition & when they appear.
- π§ Anti-join Patterns β NOT EXISTS vs LEFT JOIN/IS NULL.